The present invention relates, in general, to electronics, and more particularly, to methods of forming semiconductor devices and structure.
In the past, the semiconductor industry utilized various methods and structures to produce voltage reference circuits. As semiconductor technology continues to advance, there is a trend to lower and lower supply voltages and reference voltages in all circuit technologies. The lower supply voltages made it difficult for prior reference voltage circuits to provide the desired low reference voltage values. One example of such a voltage reference circuit was disclosed in U.S. Pat. No. 3,617,859 issued to Dobkin et al on Nov. 2, 1971, which is hereby incorporated herein by reference. As illustrated by the Dobkin et al patent, prior reference voltage circuits generally required several levels of base-emitter (Vbe) voltage drops in order to produce the desired reference voltage value. The large number of Vbe voltage drops made it difficult to produce the desired low reference voltage value from the low supply voltage. Additionally, the prior reference voltage circuits required numerous transistors and resistors to generate the reference voltage and to provide temperature compensation. These additional components added additional cost and process sensitivities.
Accordingly, it is desirable to have a reference voltage generator that operates at low supply voltages, that forms a low reference voltage value, that reduces the number of components, and that has a lower manufacturing cost.
For simplicity and clarity of illustration, elements in the figures are not necessarily to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well known steps and elements are omitted for simplicity of the description. As used herein current carrying electrode means an element of a device that carries current through the device such as a source or a drain of an MOS transistor or an emitter or a collector of a bipolar transistor, and a control electrode means an element of the device that controls current through the device such as a gate of an MOS transistor or a base of a bipolar transistor. Although the devices are explained herein as NPN devices, a person of ordinary skill in the art will appreciate that PNP devices are also possible in accordance with the present invention.